1. Field of the Invention
The present invention relates to a tape carrier for semiconductor chips and, more particulary, to a tape (or film) carrier with a specific configuration that can prevent semiconductor chips from being damaged by electrostatic discharge (ESD) during the manufacturing process.
2. Description of the Prior Art
Tape automated bonding method (TAB) is a wireless bonding method for packaging semiconductor chips. In this bonding method, a metal foil is chemically etched to form finger-like leads which are then bonded to the electrodes of chips. The finger-like leads are formed on an insulating resinous film of a tape carrier (see U.S. Pat. No. 3,689,991). In the tape automated bonding method, holes for receiving chips and finger-like conductor leads are longitudinally arrayed on a long length of tape carrier. The conductor leads are formed by etching a film of a metal, such as a copper foil, which has been previously laminated on a tape. One end of each lead is bonded to an electrode bump on a semiconductor chip. After mounting semiconductor chips in this way, the tape carrier makes contact with, or is rubbed by, a reel for winding up the carrier or other device. Then, electrostatic charges are accumulated on the carrier, so that the potential on it is raised. If any conductor lead on the tape carrier makes contact with an object that is placed at a different potential, then the potential difference destroys oxide layers in a semiconductor chip.
In order to prevent such damage by electrostatic discharge, charged particles have been sprayed against conductor leads, or conductor leads have been brought into contact with a conductive material so as to remove electrostatic charges from the surface of the tape carrier. These two proposals are effective if all conductor leads are treated. However, where chips are successively held on a long length of tape moving at a high speed, it is difficult to completely remove electrostatic charges from all of the chips.
A carrier tape is known which has a conductor pattern to short-circuit all finger-like conductor leads connected with electrodes of tips in order to prevent such damage by electrostatic discharge (see Japanese published unexamined utility model application No. 17737/1986).
The above carrier tape, however, gives rise to difficulties in electrically testing semiconductor chips mounted on the carrier tape because all the finger-like leads are short-circuited.